Preeclampsia is a major contributor to maternal and perinatal morbidity and mortality. Prevention and treatment require an understanding of both pathophysiology and clinical characterization. The Data and Clinical Core centralizes participant recruitment, data collection, data management, protocol implementation for clinically related projects within the Program Project. Specifically, these activities will entail recruiting, over a four-year period, an estimated 600 overweight (based upon pre-pregnancy measures) and 100 normal weighted nulliparous pregnant women without prior evidence of preexisting hypertension and with singleton gestations from Magee-Womens Hospital in Pittsburgh. Baseline clinical data will be obtained between 10 and 15 weeks gestation and additional biological specimens will be collected throughout the pregnancy. Approximately 100 of the recruited participants will be cross-enrolled in a randomized controlled clinical trial comparing L-arginine and placebo for 3 weeks beginning at 14 -16 weeks of gestation for intermediate outcomes in support of Projects II, III, and IV (Roberts, Hubel, and Gandley). Furthermore, 25 obese women with severe preeclampsia and 25 lean women with severe preeclampsia will be studied crosssectionally at labor and delivery (for Projects II, III, and IV). Women undergoing Caesarian- section deliveries will be recruited for collection of adipose tissue and placental samples (for Project IV, Gandley). The Clinical Data Core staff will be responsible for participant recruitment, data collection, and quality assurance. The Core will also characterize women with preeclampsia using a strict set of diagnostic criteria and a jury of clinical experts. Data will be organized and maintained using the expertise within the Center for Research on Health Care, Data Center. The Core will continue to build on current success. To date, in the Program Project, we have enrolled over 4000 women and have identified almost 900 preeclamptic women. We are confident in our abilities to continue successful recruitment of participants and maintaining quality data to support clinical projects in the Program Project.